“这是我唯一可以做的”能否翻译为"that's what I can only do"?

that's what I can do only.

that's the only thing I can do.

I will never disappoint you.

别用only在what之前加just

That's the only thing that I can do.
这是我唯一可以做的.

I will never disappoint you.
我永远不会令你们失望的.
disappoint用主动，有令某人失望的意思。

that's what I can do only 。
第二句是对的

That's the only thing I can do.
I will never disappoint you.
最简洁且正确的说法。

"这是我唯一可以做的"
对朋友，认识的人：that's the only thing I can do.
对客户，商务场合：that's what we can do.

"我永远不会令你们失望的"
i will never let you down